Expansible mandrel for driving molds for concrete piles



April 14, 1959 Y w. H. coBl 8 EXPANSIBLE MANDREL FOR DRIVING MOLDS FORCONCRETE FILES Filed May 29, 1953 V 6 Sheets-Sheet 1 April 14, 1959 w,c051 2,881,592

EXPANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE; FILES Filed May 29.1955 e Shets-Sheet 2 zkmebg [Ill/II April 14, 1959 2,881,592

EXRANSIBLE MANDREL FOR DRIVING MOLDS FQR CONCRETE PILES Filed May 29,1953 +1. cos;

6 Sheets-Sheet '5 April 1959 w. H. COB! 2,881,592

EXFANSIBLE MANDREL FOR DRIVING MOLDS FOR CONCRETE FILES Filed May 29.1953 6 Sheets-Sheet 4 A; f0 Z3 53 5/ g 36 III/III] w. H. COB! A ril 14,1959 EXPANSIBLE MANDREL FOR DRIVINQ, MOLDS FOR CONCRETE PILES eSheets-Shet 5 Filed May 29, 1953 Filed may 29. 1953' April 14, 1959wQi-l. COBI 2, EXPANSIBLE MANDREL FOR DRIVING oms FOR CONCRETE FILES eSheets-Sheet 6 United States Patent EXPANSIBLE MANDREL FOR DRIVING MOLDSFOR CONCRETE PILES Application May 29, 1953, Serial No. 358,357 24Claims. (Cl. 61-79) The invention relates to expansible pile drivingmandrels, and particularly to expansible and contracta-ble mandrels orcores capable of insertion into the empty shell or mold for a concreteor cast-in-place pile and of driving the shell into the ground underhammer blows.

The invention particularly relates to mandrels of this type which havecome to be known aspneumatic mandrels and in which the expansion iscaused by the application of fluid pessure to container means within themandrel.

It is a principal object of the invention to provide a. mandrel of thepneumatic type, comprising annularly arranged segments or quadrantscontacting the inner surface of the shell or mold, and in which theforces from thte hammer blows are substantially evenly distributed overthe cross-sectional area of the mandrel at any point along its lengththereby insuring a substantially straightline driving of the pile intothe ground, at least to the extent permitted by the nature of thestrata.

It is another object of the invention to provide such a mandrel in whichthe longitudinal elements will be firmly positioned within the shell inthe expanded condition of the mandrel to insure stable operation.

It is a further object to provide an expansible and contractable mandrelwhich can be effectively expanded by a lower fluid pressure per unitarea than in previous arrangements.

It is a more specific object to provide a stronger, inflatable, flexiblecontainer than was previously provided for expanding the mandrel, andwhich is subject to less wear, by depending for its effective actionupon a change of its cross-sectional shape from deflated to inflatedcondition and substantially avoiding any expansion or stretching of thewall material of the container during such action.

It is still another object to simplify the construction and assemblageof such a mandrel by reducing the number of parts and simplifying theiradjustments for operation.

In accordance with a feature of the invention, the mandrel is made up ofa series of annular arranged segments or quadrants extending throughoutthe length of the mandrel for contacting the inner surface of the shellof the pile, and a series of annularly arranged flexible container meansalternating with the segments and adapted to apply circumferentiallyeffective pressures to the intermediate segments, when inflated. Thuseach segment will be forced outward into contact with the shell underthe influence of a force that is the resultant of the twocircumferential forces applied thereto by two adjacent containers. Inthis manner all three sides of a segment will be subjected to opposingforces during operating condition and the segment thus will be heldfirmly in position. Similarly each container will be held firmly inposition by two adjacent segments, the great friction between thesegments and the container surfaces positively eliminating any shiftingof the container in the radial or even the lengthwise direction of themandrel Ice 2,881,592

during the rough driving operation. Thus the container means, instead ofbeing in the form'of a single tubeu'nit engaging inner corners of all ofthe mandrel segments, comprises a plurality of tube units, one tube unitbetween every two adjacent segments. With this arrangement each tubeunit will be in contact with large surfacesof two segments, thusrequiring a comparatively low inner specific fluid pressure to producethe necessary force between the segments and the shell.

In accordance with another feature the individual container tubes are incontinuous contact with the adjacent segment surfaces even in deflatedcondition. Thus the change in tube volume from deflated to inflatedcondition will be a minimum and it is possible to avoid any appreciableelongation of the tube wall during inflation, thereby increasing thelife of the tubes. Furthermore, without the need of stretching, the tubemaybe covered on' the outside with a non-stretching but flexible layerwhich may be of a much tougher and better wearing-material thentheliquid or gas impervious material in the tube wall proper.

In accordance with still another feature each tube unit is produced orcured in a flattened shape corresponding to its shape in the mandrelduring deflated condition. Thus the springs for contracting, or forcinginwardly, the mandrel segments need not compress the tubes, and may beof comparatively light construction. This feature also greatlysimplifies the assembling and dismantling of the mandrel inasmuch as theflat deflated tube may be readily laid in position between the segmentswithout the need of tampering or locking down by'bolts or tools.

In accordance with yet another feature the contracting spring means areradially disposed to apply radially directed pressure to the segments.This feature permits of a simpler construction as well as of easieraccess "to the springs and assembling bolts. 1

Other features and advantages of the invention will be hereinafterdescribed and claimed:

The following detailed description should be read in conjunction withthe attached drawings, which show a preferred embodiment of theinvention. It should however be understood that the invention is notlimited by the terms or expressions used in this description, nor by thespecific details or arrangements of parts shown in the drawing. Thescope of the invention in its various aspects is defined by the attachedclaims.

In the drawings:

Fig. 1 is a vertical sectional view of the upper portion of theexpansible mandrel or core showing the mandrel in place within the upperportion of the shell or mold and expanded ready for use.

Fig. 2 is a similar vertical sectional view of the lower portion of theexpansible mandrel, showing the mandrel in place within the lowerportion of the shell and expanded ready for use. The sections of Figs. 1and 2 are taken along a diametrical plane through the mandrel asindicated by line 11 of Fig. 3.

Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 1.

Fig. 9 is similar to Fig. 3, except that it shows the mandrelcontracted.

Patented Apr. 14, 1959 L Fig. 10 is similar to Fig. 5, except that itshows the mandrel contracted.

Fig. 11 is similar to Fig. 6 except that it shows the mandrelcontracted.

The following are detail Views of certain parts: ,Fig. 12 is taken alongline 12-12 in Fig. 3;

Fig. 13 is taken along line 13-13 in Fig. 4;

Fig. 14 is similar to Fig. 13 except that it shows the relation of theparts when the mandrel is contracted;

Fig. 15 is partly in cross-section and is taken along line 15-15 in Fig.4;

Fig. 16 is taken along line 16-16 in Figs. 4 and 8;

Fig. 17 is a side view of the parts in Fig. 16;

Fig. .18 is partly in cross-section and is taken along line 18-18 inFig. and

Fig..19 isa cross-sectional view taken along line 19-19 in :Fig. 18.

The drawings show in general an expanded mandrel in operative positionwithin a pile shell or mold 10, except forFigs. 9, 10, 11 which show themandrel contracted within the shell 10. The shell is of the corrugatedtype, having corrugations running .helically and in immediate successionalong the entire length.

In the embodiment shown in the drawing the mandrel is made up of foursimilar segments or quadrants 12, 14, 16, 18which extend through theentire length of the mandrel. Each segment includes an angle member 21and a curved plate 22 which is welded along its entire length to the twoedges of the angle member 21. The member 21 and the plate 22 may be ofsteel drawn to the desired shapes and dimensions. Both the members 21and the plates 22 receive the force from the hammer blows at their upperends and may transmit the force through their entire length to thebottom end of the mandrel. When the length of the mandrel exceeds themanufacturing lengths of these members and plates, successive portionsare welded together, so that each segment forms one continuousstructure.

Ascan be seen in Fig. 6 where the four segments are shown in theexpanded condition of the mandrel and in contact with the shell 10, thefour plates 22 are separated by spaces 23 between their edges, whichallows for the contraction of the mandrel, as shown in correspondingFig. 11.

As will further appear from Fig. 6 the angle irons or members 21 arewelded to the plates 22 well inside the edges of the plates so that aspace 24 is formed between adjacent angle irons 21 which is wider thanthe space 23. Thus when the mandrel is collapsed, as shown in 'Fig. 11,and the plates 22 engage, the space 24 still remains though of muchreduced width.

In the four spaces 24 between the angle irons 21 pressure containers32,34, 36 and 38 are located; they are tubular and extend through thelength of the mandrel, except for short distances at top and bottom.

Each tubular container is mainly of flexible material 41 (see Figs. 18and 19-) impervious to the fluid used for the pneumatic expansion of themandrel, and the outer surface is covered by a hard wearing fabric 42,woven thereabout. The material 41 is preferably vulcanized rubber andthe fabric 42 is of thread with a large percentage of nylon fibre andthis may further be coated with a plastic covering. Other materials maybe found suitable for these purposes. 'Each of the tubes or containers32, 34, 36 and 38 is closed at its upper end by an end plug 45 throughwhich the pressure fluid may be admitted. The bottom of each tube isclosed by a similar end plug 46, which however 'hasnopassage for thepressure fluid.

In the manufacture of the tubular containers, the tubes are formed andcured in the flat shape shown in Fig. 11, so that, when the mandrel iscontracted, they fit the narrowed space 24 without exerting anyappreciable pressure on the angle irons 21. The inflated condition ofdhe tubes 32, 34, 36, 38 is shown in Fig. 7, the tubes approaching thecylindrical shape without the tube walls being substantially elongatedperipherally.

Compression springs 50 and bolts 51 are distributed at intervals of afew feet along the whole length of the mandrel. Such a bolt is shown inFig. 6 for the expanded condition and in Fig. 11 for the contractedcondition. For the mounting of a bolt two triangular filler blocks 53are welded in position in the angles of the angle irons 21 of thediametrically opposed segments or quadrants 12 and 16 and suitable holesare provided in the irons 21 and the blocks 53 for passing of the boltbetween adjacent tubes 32, 34 and 36, 38. A spring 50 surrounds each endof the bolt and sets on the shoulder of the widened hole 54 in the block53. Each spring is tightened by a nut and washer 55 on the end of thebolt. Openings or holes 58 in the plates 22, large enough to pass thesprings and washers 55, permit of the insertion of the bolts and thetightening of the nuts.

Figs. 2 and 7 show other bolts 51 and filler blocks 53 for the segments14 and 18, these bolts thus being at right angles to the similar boltsbetween segments 12 and 16, and alternating with them throughout thelength of the mandrel. These latter bolts between segments 14 and 18thus pass between adjacent tubes 34, 36 and 38, 32.

In the contracted condition of the mandrel, shown in Fig. 11, thesprings 50 still have suflicient compression to force the edges ofadjacent plates 22 into firm contact, thereby insuring the safeinsertion into and removal from the pile shell 10 of the whole mandrel.

It may thus be seen that the mandrel is expanded by four tubularpneumatic containers located in a circle with, and alternating with,four segments of the mandrel. During inflation each segment or quadrantis acted upon by two containers on two of its sides and will be forcedoutward into engagement of its third side, the plate 22, with the innersurface of the pile shell by the radial resultant of the two angularlydirected forces applied by the pressure containers. Thus duringoperation the segments will be held firmly in position relatively to oneanother and will be evenly distributed relatively to the .shell. In thismanner an even distribution between the four segments of the forcesapplied by the strokes of the driving hammer is insured duringoperation, so that the pile may automatically be driven into the groundalong a straight line, in so far as permitted by the compositions of thestrata.

It may further be seen that the mandrel is contracted by contractingspring means which include bolts and springs connecting alternate,opposite segments together. During deflation of the containers thespring means act along radial lines upon the segments and thus force thesegments directly towards the center of the mandrel until their edgescome into firm engagement, so that the mandrel along its entire lengthmay readily clear the corrugated shell during removal therefrom.

Though the present embodiment of the invention is shown and describedherein as a mandrel comprising four segments, four tubes and contractionspring means between opposed segments, it should be understood that,without a departure from the spirit and scope of the invention, themandrel may comprise six segments and six tubes, or a larger even numberof segments and tubes with contraction spring means between opposedsegments.

It should further be understood that the shape of the plates engagingthe inner surface of the shell may differ from that shown in the drawingand may be made to conform to other shapes of the shell, than thecircular shape shown. Thus the plates may be fiat to conform with asquare shell, or they may be of an angular crosssection to conform withpolygonal cross-sections of a shell with more than four corners.

Considering now more specific features of the mandrel, each curved plate22 is reenforced at its upper end by a short similarly curved protectingplate 61 welded along its edges to the outside of the plate 22.

In the present instance of :1 corrugated shell, the plates 22 havewelded to their outer surfaces a series of half round helix bars 62, asshown in Fig. 2, which are disposed along helical lines to fit into thegrooves of the helically corrugated shell. The sets of circumferentialbars are placed at intervals of about a foot or more along the length ofthe mandrel. By this means the driving force of the hammer blows may bepartly distributed over the whole length of the shell to overcome thefriction with the ground during driving.

The top assembly of the mandrel includes a drive head 70, shown in Fig.1 which is in the form of a cylindrical block with a depression 71 inthe top surface for receiving the metal encased wooden hammer cushion72, and with a depression 73 in the bottom surface fitting loosely overthe protecting plates 61 of the mandrel. The head has two parallel holes74 through the body portion thereof. 3

Two mild steel buffer plates-75 are'positioned against the bottom of thedepression 73 and engage the upper aligned end surfaces of the angleirons 21 and plates 22 for evenly distributing the hammer blows to theseelements during operation.

The drive head 70 is loosely connected to the upper end of the mandrelproper by a lifting bolt 80 fastened in a central hole 81 in the drivehead 70 by means of spherically surfaced washers 82, 83 held againstspherically surfaced shoulders in the hole 81 by a nut 84 on theshouldered bolt 80.

The lower end of the bolt extends a short distance into the interior ofthe mandrel where it carries a spider 85 having a hub portion forfastening to the bolt and two pairs of flat wings 86, 87 extending intothe spaces 24 between the angle irons 21. As may be seen in Figs. 1, 3and 12 the wings 86, 87 extend in under and clear two pairs ofcross-bolts 88, 89 which cross the spaces 24 and pass through and beyondholes in the opposed faces of the angle irons 21 and in the associatedplates 22 and 61 and extend a short distance beyond the plates 61 in theexpanded condition of the mandrel. Each bolt has a head at one end;while the other end is tapered for easy passage through the plates atthe time of assembly. Short screws 88', 89' are placed through saidother ends of the bolts 88, 89 and are provided with nuts (as shown inFigs. 3 and 12) to prevent the bolts from being shaken out during theoperations. The pair of cross bolts 88 are placed at a higher level thanthe pair 89 to clear them. When the mandrel is deflated and is to belifted out of a shell which has been driven in place a steel cable ispassed through the holes 74 in the drive head and up about the hammerbase of the driving rig, and the mandrelis lifted bodily up into theleads of the driving rig. After the drive head 70 has been raised ashort distance, an inch more or less, the two pairs of wings 86, 87 willengage the corresponding pairs of cross-bolts 88, 89 whereupon theentire mandrel will rise with the drive head. It will be noted that theupper edges of the spider wings are sloped downward inwardly, therebyapplying an inward force to the cross-bolts during lifting in case theupper free end of the mandrel has not been sufficiently contracted. Bymeans of the spherical mounting of the lifting bolt 80 in the driveheada certain freedom of self-adjustment between the drivehead and the topof the mandrel is available during the rough lifting operations. Theupper and lower nuts on bolt 80 are preferably of the type known aselastic stop nuts, which may be depended upon to lock themselves on tothe bolt.

The bottom assembly of the lower end of the shell the mandrel iscontained by and the boot 11 welded thereto. As shown in Figs. 2 and 8 aheavy plate 90 is placed between the bottom of the boot and the alignedbottom cross-sectional surfaces of theangle irons 21 and ture 45includes a piece tubular container, say container plates 22 to receivethe forces of the hammer blows and impart them to the boot. The plate 90has a central hollow upright 91, which at its upper end carries acrossbar 92 which extends in both directions through snug holes indiametrically located angle irons 21, so that, when the mandrel isinserted into or removed from the shell, the plate 90 will follow as apart thereof. The hole 93 in the upright is slightly oblong in order torelieve the crossbar 92 from the forces of the hammer blows duringdriving. The bar 92 passes snugly through holes in the angle irons 21when these move in and out during the expansion and contraction of themandrel. One end of the bar 92 is slightly tapered for easyinsertion'through the associated holes, and the other end is slotted andcarries a key projection 94, as shown in Figs. 16 and 17. Holes 95 and96 in plates 22 register with the ends of bar 92, the hole 96 having aslot 97 in its upper side. The bar is normally locked in position byhaving its key 94 on the under side, but when it becomes de sirable toremove the bar the key is turned upward, say by a screwdriver acting inthe end slot, and the bar may be driven out by pushing it with a rodthrough the hole 95.

Now referring to specific features of the pneumatic equipmentillustrated, the fixtures 45 and 46 at the upper and lower ends of thetubular containers 32, 34, 36, 38 are substantially similar.

As will appear most clearly from Figs. 18 and 19 a fixof tubing 101having at its upper end a nipple 102 for receiving a small pneumatichose 103, a piece of rod 104, a plate welded alongits edges to tubing101 and rod 104 and two clamping plates 106 and 107, which may beclamped to the walls of a 32, by means of a plurality of short bolts108. In assembling these parts the tubing 101, rod 104, plate 105 andthe inner surface of the tubular container, say 32, are coated with aliquid sealing compound; the tubing, plate and rod are placed as a unitinside the opposite faces of the flat end of the tube 32; the plates106, 107 are forced down from opposite sides against the outside flatsides of tube 32; and the plates are screwed tight and thereby force theportions of tube 32 tight about the tubing, plate and rod. With theproper width of the clamping plates 106 and 107 a tight end seal for thetube 32 is obtained which will withstand pressures considerably higherthan the normal operating pressure applied to the pneumatic system. Thetubing 101 affords access to the interior of the tube 32 for thepressure fluid.

The plate 106 is extended upward beyond the end of the tube 32 into anear 111 having a hole into which is welded a bushing 112 which extendsacross the space 24 and is of a length to fit between the faces of twoangleirons 21 when the mandrel is contracted, as shown in Fig. 10. Acrossrod 113 extends through the bushing 112 and through snug holes inthe adjacent faces of the angleirons. The crossrod 113 moves freelythrough the angle irons during inflation and deflation and is of suchlength as not to interfere with the plates 22 when the mandrel iscontracted. If desired, one pair of diametrically disposed rods 113 maybe set at a slightly higher level than the other pair to avoidinterference between their ends.

The fixtures 46 at the bottom of the tubular containers differ from thefixtures 45 mainly in that they afford no passage for the pressurefluid, because the nipple 102 is closed by a plug 115 which may bescrewed in with sealing compoun The upper fixtures 45 connect theirassociated tubular containers 32, 34, 36, 38 through the individualhoses 103 to a manifold or fluid distributor which, as shown in Figs. 1and 4, is located in the center of the upper end of the mandrel. Themanifold is shown more in detail in Fig. 15. It comprises anintermediate tubular section 122, an upper hollow end section 123, and alower solid end section 124. Both said sections 123 and 124 are weldedto the middle section 122. The middle section has hollow projections 126extending partly downward and being threaded,to each receive a nipple127 for connection of the upper end of the corresponding pneumatic hose103. The circuit for the fluid pressure is completed through the hollowend section 123, a common nipple 128 screwed through the wall of section123, a pneumatic hose 129 which connects to a suitable nipplearrangement 130 fixedly mounted on a bracket 131 welded to the outsideof one of the upper reenforcing plates 61, the nipple arrangement havingan exterior female nipple 132 suitable for attachment of the long hoseconnection running down the rig to the control valve and the compresserin the crane.

The manifold is carried by a crossbar 140 passing through its lowersection 124 and through holes in diametrically opposite angle irons 21.The crossbar 140 is similar to the crossbar 92 near the bottom end ofthe mandrel, and reference may thus be had to Figs. 16 and 17 and therelated description for details of construction and of removal of thebar through the plates 22 when it becomes desirable to remove themanifold.

- Inasmuch as the edges of adjacent plates .22 and 61 contact each otherwhen the mandrel is contracted a clearance 150 has been provided for thenipple arrangement 130 by cutting out semicircular pieces from theplates 21 and 61 of sections 12 and 18, as shown in Figs. 13 and 14.

It will further be noted that the inward projecting corners of the angleirons 21 have been milled off attheir upper ends to provide suflicientspace for the spider '80 and the manifold 120.

In assembling the mandrel, two sections 12 and 14 are laid side by sidewith the tube container 34 between them. The distance between thecrossbolt 113 at opposite ends of the tube is several inches shorterthan the distance between the corresponding holes in the flat sides ofthe flatirons 21. Thus the tube is attached first at one end byinsertion of the bolt 113 into the fixture 45 and through the oppositefaces of the angle-irons 21, and then the tube is stretched so that theother bolt may be inserted in the fixture 46 and through the angle-irons21 at their other end. Four more bolts 113 are then inserted and thetubes 32 and 36 are stretched and placed on the bolt. The manifold withhoses attached are then put in position, three hoses 103 are connectedto their tubes, the fourth hanging free, and tube 129 is connected tofixture 130.

Then two sections 16 and 18 are laid side by side with the tube 38stretched between them on bolts 113 at opposite ends. This assemblage isthen laid on the first assemblage with the four protruding bolts 113 andthe fourth hose 103 is connected to the tube fixture 45 of tube 38. Thebar 140 is then driven in the manifold ward.

Then all the compression bolts 51 are inserted and their springstightened. The bottom plate is put in place and its bar 92 inserted andlocked in position by turning its key downward. The drive head 70 withthe bolt 80 and spider 85 attached is placed in position over the upperend of the mandrel and the four bolts 88, 89 put in place to looselyattach the drive head to the mandrel. The mandrel then is ready foroperation under fluid pressure.

Mandrels of this type may be used under greatly varying conditions andwith shells of greatly varying lengths 120 and locked by turning its keydown- .and cross-sections. The dimensions of the mandrel and its partstherefore may vary greatly. The mandrel may be designed for shells 100feet or more in length.

The fluid pressure is preferably obtained from an air compressor, andthe pressure for the longest mandrels meed not exceed 80- lbs/sq. in.The compression springs position through I may be tensioned to 300 lbs.and may be spaced 5 feet apart, more or less, along the mandrel.

When the mandrel is collapsed the half round helix bars 62 on itsoutside surface clear the inside of the corrupated shell by the least 4all around, and the expansion may amount to an increase in diameter ofthe mandrel of about an inch and a half. It will, of course, beunderstood that the foregoing pressures and dimensions are merelyexamples of those that may be employed.

The terms and expressions which I have employed are used as terms ofdescription and not of limitation, and I have no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but recognize thatvarious modifications are possible within the scope of the inventionclaimed.

I claim:

1. An expansible mandrel for insertion into a metal shell to receivehammer blows for driving the shell into the ground, said mandrelincluding a plurality of segments each having a rim portion engageablewith said shell and an angular frame portion extending inwardly fromsaidrim portion, the angular frame portion of each segment having facesangularly disposed with respect to each other, and the frame portion ofeach segment being adjacent to frame portions of other segments, aplurality of flexible pressure-containers each disposed between faces ofa pair of adjacent frame portions for applying pressure to said faces toproduce resultant forces moving said rim portions into engagement withsaid shell, and resilient means opposing said forces.

2. An expansible mandrel for insertion into a metal shell to receivehammer blows for driving the shell into the ground, said mandrelcomprising a plurality of segments each having a rim portion engageablewith said shell and an angular frame portion extending inwardly fromsaid rim portion, the angular frame portion of each segment having facesangularly disposed with respect to each other, and the frame portion ofeach segment being adjacent to frame portions of other segments, and aplurality of flexible pressure-containers each disposed between faces ofa pair of adjacent angular frame portions for applying pressure thereto.

3. An expansible mandrel for insertion into a metal shell to receivehammer blows for driving the shell into the ground, said mandrelcomprising a plurality of segments each having a rim portion engageablewith said shell and an angular frame portion extending inwardly fromsaid rim portion, the angular frame portion of each segment having facesangularly disposed with respect to each other, and the frame portion ofeach segment being adjacent to frame portions of other segments, aplurality of flexible pressure-containers each disposed between faces ofa pair of adjacent angular frame members, resilient means acting uponsaid mandrel segments to urge them into inwardly retracted positionswherein said rim portions are out of engagement with said shell, and.means for directing fluid-pressure to said containers for forcing saidsegments outwardly to engage said rim portions with said shell.

4. An expansible mandrel as defined in claim 3, wherein said resilientmeans comprises bolts extending diamettrically through oppositelydisposed mandrel segments and spring means cooperating with said boltsfor urging said oppositely disposed segments inwardly toward each other.

5. A mandrel as defined by claim 1 wherein said pressure containers aresubstantially flattened when uninflated and are expansible by change ofshape under fluid pressure without substantially stretching of theirmaterial.

6. A mandrel as defined by claim 1 wherein each of said pressurecontainers is attached at its ends to faces of adjacent frame portionsof said mandrel segments.

i said segments, means 7. A mandrel as defined by claim 4, inclu ingapin passing through said pressure-directing means and also throughdiagonally opposite mandrel segments for attaching said directing meansto said segments.

8. Amandrel as plate at the lower ends of said segments, an extensionfrom said plate, and a pin projecting through said ex-' tension andthrough diagonally opposite mandrel sec-' tions for attaching said plateto said segments.

- 9. A mandrel as defined by claim 1, including a drive head overlyingsaid mandrel through certain faces of angular frame portions of said.mandrel segments, other pins extendingtransversely of thefirst-mentioned pins through other faces of said angular frameportions,and means depending from said drive head for engaging said pins to raisethe mandrel out of the shell when said drive head is lifted.

10. A mandrel as defined by claim 1, including a drive head overlyingsaid mandrel segments, pins extending through certain faces of angularframe portions of said mandrel segments, other pins extendingtransversely of the first-mentioned pins through other faces of saidangular frame portions, and means. depending from said drive head forengaging said pins to raise the mandrel out of the shell when said drivehead is lifted, said depending means having arms with inclined surfacesunderlying said pins to both raise said mandrel segments and insureinward movement thereof to disengage said rim portions from the shell assaid drive head is lifted.

11. A mandrel as defined by claim 1, including a drive head overlyingsaid mandrel segments means depending from said drive head into acentral space between said mandrel segments and adjacent thelongitudinal axis of said mandrel, and means extending transversely fromsaid depending means for raising said segments out of the shell as thedrive head is lifted.

12. A mandrel as defined by claim 1, including a drive head overlyingsaid mandrel segments, means depending from said drive head into acentral space between said mandrel segments and adjacent thelongitudinal axis of said mandrel, and means extending transversely fromsaid depending means for raising said segments out of the shell as thedrive head is lifted, and curved bearing means between said dependingmeans and said drive head to enable self-adjustment of said dependingmeans with respect to said drive head during lifting of said segments.

13. An expansible mandrel for insertion into a metal shell to receivehammer blows for driving the shell into the ground, said mandrelcomprising a plurality of segments disposed about a longitudinal axis ofsaid mandrel, each of said segments having a rim portion engageable withsaid shell and an angular frame portion extending inwardly from said rimportion toward said axis, the angular frame portion of each segmenthaving faces angularly disposed with respect to each other, and theframe portion of each segment being adjacent to frame portions of othersegments, a plurality of flexible pressure-containers, each disposedbetween the faces of frame portions of an adjacent pair of said mandrelsegments and located between said axis and the rim portions of forsupporting said pressure-containers from said mandrel segments, andmanifold means for directing fluid pressure to said pressure-containersfor applying force to said frame portions and moving said segmentsoutwardly to engage said rim portions with said shell.

14. An expansible mandrel for insertion into a metal shell to receivehammer blows for driving the shell into the ground, said mandrelcomprising a plurality of segments each having a rim portion engageablewith said shell and an angular frame portion extending inwardly fromsaid rim portion, the angular frame portion of each segment having facesangularly disposed with respect to each other, and the frame portion ofeach segment bedefined by claim 1, including a bottom tween faces of apair of adjacent segments, pins extending ing adjacent to frame portionsof other segments, a plurality of flexible pressure-containers eachdisposed beangular frame members, and means for directing fluid-pressureto said containers for forcing said mandrel segments outwardly to engagesaid rim portions with said shell, a pin passing through saidpressure-directing means and also through diametrically opposite mandrelsegments for attaching said directing means to said segments, the rimportion of one of said segments having an opening therein with a slotprojecting therefrom, and said pin having a key projection adapted topass through said slot when aligned therewith, said pin being mounted insaid pressure-directing means 7 for rotation to bring said key out ofalignment with said slot after said key has been passed therethrough.

15. A mandrel as defined by claim 1, including a bottom plate at thelower ends of said segments, an extension from said plate, and apinprojecting through said extension and through diagonally oppositemandrel segments for attaching said plate to said segments, the rimportion of one of said mandrel segments having an opening therein with aslot projecting therefrom, and said pin having a key projection adaptedto pass through said slot when aligned therewith, said pin beingrotatably mounted in said extension from said plate to bring said keyout of alignment with said slot after said key has been passedtherethrough.

16. An expansible mandrel as defined by claim 2, wherein each of saidpressure-containers is attached at an end to a bracket member having aportion extending into said end and another portion extending outwardlybeyond said end, and means projecting through the last mentioned bracketportion for attaching said container to a section of said mandrel.

17. An expansible mandrel as defined by claim 2, wherein each of saidpressure containers is substantially flat when uninflated and hasprojecting into one end thereof a plate having integral therewith a tubefor directing fluid pressure into said container, said plate also havinga portion projecting beyond said container end and forming a bracket forattachment of the container generally radial spaces to a segment of saidmandrel.

18. An expansible mandrel as defined by claim 2, wherein each of saidpresure containers is substantially fiat when uninflated, bracketmembers attached to opposite ends of said containers for connecting themto segments of said mandrel, and tubes integral with certain of saidbracket members and projecting into said containers for directing fluidpressure thereinto.

19. An expansible core for driving pile shells comprising a plurality ofleaf structures extending longitudinally of the core and arranged aroundabout the core axis with therebetween and hoses extending longitudinallyof the core and along between adjacent leaf structures within saidspaces respectively, whereby upon filling such hoses with fluid underpressure the leaf structures may be forced outwardly of the core andinto contact under pressure with the interior surfaces of a pile shell.

20. An expansible core for driving pile shells comprising a plurality ofleaf structures extending longitudinally of the core and arranged aroundabout the core axis with generally radial spaces therebetween, and fluidpressure expansible means extending longitudinally of the core alongbetween adjacent leaf structures within said spaces respectively, theleaf structures each comprising a portion of arcuate cross-section forengagement with the interior surface of the pile shell and two plateportions extending inwardly from the longitudinal edges of said arcuateportion respectively, the expansible means each being positioned toengage one of such plate means on one leaf structure and one of suchplate means of another of said leaf structures.

21. An expansible core for driving pile shells comprising a plurality ofleaf structures extending longitudinally of the core and arranged aroundabout a central space, each of said leaf structures having a generallysector shaped cross-section, fluid pressure expansible means extendinglongitudinally of the core along between adjacent leaf structureswhereby upon filling such expansible means with fluid under pressure theleaf structures may be forced outwardly into contact under pressure withthe interior surfaces of a pile shell, a core head for applying impactsto the upper ends of said structures, and mechanical means connected tosaid core head 1 and extending down in said central space withconnections to said leaf structures for retracting the latter when thecore head is raised.

22. An expansible core for driving pile shells comprising a plurality ofleaf structures extending longitudinally 1 of the core and arrangedaround about the core axis, a radially extending space being providedbetween at least two of said leaf structures, each of said leafstructures having a cross-sectional outline of generally sector shape,

and a hose extending along between two adjacent leaf 20 structures andnormally contained within said space whereby when such hose is filledwith fluid under pressure the leaf structures may be forced outwardly ofthe core axis.

23. An expansible mandrel for insertion into a metal 25 shell to receivehammer blows for driving the shell into the ground, said mandrelincluding a plurality of opposited disposed segments each engageablewith a portion of the shell diametrically opposite the portion engagedby the other of said segments, each of said segments comprising anarcuate plate for engagement with a portion of the shell and a rigidpressurereceiving member ing from one of said segments to the other andspring means at opposite end portions of said bolt and bearing againstportions of said mandrel segments.

24. An expansible mandrel as defined in claim 23, wherein said segmentsare diametrically disposed with respect to each other with anintervening space therebetween, and the bolt extends through bothsegments and the intervening space.

References Cited in the file of this patent UNITED STATES PATENTS2,313,625 Cobi Mar. 9, 1943 2,321,146 Jones June 8, 1943 2,625,015 CobiJan. 13, 1953 2,684,577 Smith July 27, 1954

